*2.9. Fourier Transform Infrared Spectroscopy*

*2.9. Fourier Transform Infrared Spectroscopy* FTIR provides information about the molecular structure and composition of the film, it also provides valuable information about the degree of cross-linking in the film, which affects its mechanical properties and durability. SA and AG composite edible films loaded with the CEO were analyzed for FTIR and the absorption spectrum is shown in Figure 4. The broad spectrum at 3305 cm−1 indicates the stretching vibration of the secondary N-H amide bonds [30]. The characteristic peaks identified at 1410 cm−1 and 1600 cm−1 could have been due to the presence of sodium alginate in the film matrix, representing the symmetric and asymmetric stretching vibration of the COO-group respectively [31]. Additionally, studies have also reported that characteristic peaks identified at 1400 cm−1 and 2925 cm−1 positions could be due to the presence of sodium alginate [25]. In a previous study, it was reported that AG exhibited a characteristic peak at 2929 cm−1 in the FTIR analysis [32]. A study reported the -C=O stretching vibration of the tween 80 carbonyl group at 1735 cm−1 and 1736 cm−1 during the FTIR analysis [20]. In our current study, the film matrix exhibited a characteristic peak at 1733 cm−1 that could be ascribed to the FTIR provides information about the molecular structure and composition of the film, it also provides valuable information about the degree of cross-linking in the film, which affects its mechanical properties and durability. SA and AG composite edible films loaded with the CEO were analyzed for FTIR and the absorption spectrum is shown in Figure 4. The broad spectrum at 3305 cm−<sup>1</sup> indicates the stretching vibration of the secondary N-H amide bonds [30]. The characteristic peaks identified at 1410 cm−<sup>1</sup> and 1600 cm−<sup>1</sup> could have been due to the presence of sodium alginate in the film matrix, representing the symmetric and asymmetric stretching vibration of the COO-group respectively [31]. Additionally, studies have also reported that characteristic peaks identified at 1400 cm−<sup>1</sup> and 2925 cm−<sup>1</sup> positions could be due to the presence of sodium alginate [25]. In a previous study, it was reported that AG exhibited a characteristic peak at 2929 cm−<sup>1</sup> in the FTIR analysis [32]. A study reported the -C=O stretching vibration of the tween 80 carbonyl group at 1735 cm−<sup>1</sup> and 1736 cm−<sup>1</sup> during the FTIR analysis [20]. In our current study, the film matrix exhibited a characteristic peak at 1733 cm−<sup>1</sup> that could be ascribed to the presence of tween 80 in the film matrix; however, a little variation (from 1735 cm−<sup>1</sup> to 1733 cm−<sup>1</sup> ) could have been due to the difference in the concentration. A distinctive peak at 1456 cm−<sup>1</sup> corresponding to the phenolic group of cinnamaldehyde was observed in the FTIR spectrum that indicates the presence of CEO in the film matrix [20]. Overall, the FTIR analysis showed a good intermolecular interaction between the CEO, SA and AG.

presence of tween 80 in the film matrix; however, a little variation (from 1735 cm−1 to 1733 cm−1) could have been due to the difference in the concentration. A distinctive peak at 1456 cm−1 corresponding to the phenolic group of cinnamaldehyde was observed in the FTIR spectrum that indicates the presence of CEO in the film matrix [20]. Overall, the FTIR

analysis showed a good intermolecular interaction between the CEO, SA and AG.

**Figure 4.** FTIR spectrum of SA–AG hydrogel-based edible films; AC-1/ Control, AC-2 contains 15 μL of CEO, AC-3 contains 20 μL of CEO and AC-4 contains 30 μL of CEO. **Figure 4.** FTIR spectrum of SA–AG hydrogel-based edible films; AC-1/Control, AC-2 contains 15 µL of CEO, AC-3 contains 20 µL of CEO and AC-4 contains 30 µL of CEO.

#### *2.10. DSC Analysis 2.10. DSC Analysis*

The thermal stability of edible films refers to their ability to maintain their physical, chemical, and structural properties when exposed to elevated temperatures. Thermal stability is a critical factor for the performance and functionality of edible films, as it affects their shelf life and suitability for various food packaging applications. DSC analysis can be used to evaluate the thermal stability of edible films by measuring the temperature and heat flow during heating or cooling cycles. The DSC thermograms of the SA–AG-based composite films are shown in Figure 5. The AC-2, AC-3, and AC-4 films incorporated with CEO presented one broad endothermic peak at 70–128 °C, 72–126 °C, and 51–118 °C, respectively. This endothermic peak can be attributed to the evaporation of the residual solvent (water) that was used during the production of composite films [33,34]. After the incorporation of oil into the films, the temperature of the endothermic peak increased significantly in AC-2 and AC-3 samples, but the temperature slightly reduced in the AC-4 sample with a maximum (30 μL) of CEO. As the concentration of CEO was increased, the peak area of the AC-2, AC-3, and AC-4 samples also increased, indicating that the thermal stability of the composite films improved due to the addition of EOs. This shift could have been due to the plasticization effect of oil, which would have raised the free volume within the polymeric network and mobility of the polymeric chains as reported in the previous studies [35]. The thermal stability of edible films refers to their ability to maintain their physical, chemical, and structural properties when exposed to elevated temperatures. Thermal stability is a critical factor for the performance and functionality of edible films, as it affects their shelf life and suitability for various food packaging applications. DSC analysis can be used to evaluate the thermal stability of edible films by measuring the temperature and heat flow during heating or cooling cycles. The DSC thermograms of the SA–AG-based composite films are shown in Figure 5. The AC-2, AC-3, and AC-4 films incorporated with CEO presented one broad endothermic peak at 70–128 ◦C, 72–126 ◦C, and 51–118 ◦C, respectively. This endothermic peak can be attributed to the evaporation of the residual solvent (water) that was used during the production of composite films [33,34]. After the incorporation of oil into the films, the temperature of the endothermic peak increased significantly in AC-2 and AC-3 samples, but the temperature slightly reduced in the AC-4 sample with a maximum (30 µL) of CEO. As the concentration of CEO was increased, the peak area of the AC-2, AC-3, and AC-4 samples also increased, indicating that the thermal stability of the composite films improved due to the addition of EOs. This shift could have been due to the plasticization effect of oil, which would have raised the free volume within the polymeric network and mobility of the polymeric chains as reported in the previous studies [35].

The improved thermal stability of the composite hydrogel-based films indicates that there were strong intermolecular interactions between the CEO and composite material, which could potentially influence the mechanical properties of the films. The previous studies suggested that the incorporation of *Origanum vulgare* L. and *Matricaria recutita*

of CEO, AC-3 contains 20 μL of CEO, and AC-4 contains 30 μL of CEO.

polymeric films [36,37].

**Figure 5.** DSC analysis of SA–AG-based composite edible films; AC-1/ Control, AC-2 contains 15 μL **Figure 5.** DSC analysis of SA–AG-based composite edible films; AC-1/Control, AC-2 contains 15 µL of CEO, AC-3 contains 20 µL of CEO, and AC-4 contains 30 µL of CEO.

essential oil caused a change in endothermic peaks, indicating the thermal stability of the

As per previous reports, the incorporation of *Origanum onites* L. essential oil reduced the heat transitions due to evaporation, as evidenced by changes in endothermic peaks. This could be due to the molecular structure of the essential oil that caused the changes in the overall chain mobility of the polymer matrix, as reported in previous studies [38,39].

*2.11. Antioxidant Potential* The antioxidant activity of hydrogel-based films can help to protect the food packaged within the film from oxidation, which can cause the food to spoil or lose quality. The addition of essential oils to edible films can increase their antioxidant potential, and can The improved thermal stability of the composite hydrogel-based films indicates that there were strong intermolecular interactions between the CEO and composite material, which could potentially influence the mechanical properties of the films. The previous studies suggested that the incorporation of *Origanum vulgare* L. and *Matricaria recutita* essential oil caused a change in endothermic peaks, indicating the thermal stability of the polymeric films [36,37].

help to protect the packaged food from oxidation and extend its shelf life. Essential oils are concentrated plant extracts that contain a variety of antioxidants, such as phenolic compounds, terpenes, and flavonoids [40]. In the current study, the antioxidant activity of the different samples of edible films based on SA and AG was assessed and the results are shown in Figure 6. The hydrogel-based films showed a significant increase in the As per previous reports, the incorporation of *Origanum onites* L. essential oil reduced the heat transitions due to evaporation, as evidenced by changes in endothermic peaks. This could be due to the molecular structure of the essential oil that caused the changes in the overall chain mobility of the polymer matrix, as reported in previous studies [38,39].

#### DPPH radical scavenging activity with increasing the concentration of the CEO. Similar *2.11. Antioxidant Potential*

results were obtained for the ABTS radical scavenging activity of the SA–AG-based composite film samples. The films incorporated with CEO exhibited more antioxidant activity compared with the control. This could have been due to the presence of different bioactive compounds in the CEO, primarily cinnamaldehyde, contributing to the overall antioxidant potential of the edible films [41]. Xu et al. [42] found similar results in which the antioxidant activity of the chitosan-gum arabic films increased with the addition of CEO. Furthermore, many studies have reported an increase in the antioxidant activity of edible films when incorporated with essential oils [43–45]. The antioxidant activity of hydrogel-based films can help to protect the food packaged within the film from oxidation, which can cause the food to spoil or lose quality. The addition of essential oils to edible films can increase their antioxidant potential, and can help to protect the packaged food from oxidation and extend its shelf life. Essential oils are concentrated plant extracts that contain a variety of antioxidants, such as phenolic compounds, terpenes, and flavonoids [40]. In the current study, the antioxidant activity of the different samples of edible films based on SA and AG was assessed and the results are shown in Figure 6. The hydrogel-based films showed a significant increase in the DPPH radical scavenging activity with increasing the concentration of the CEO. Similar results were obtained for the ABTS radical scavenging activity of the SA–AG-based composite film samples. The films incorporated with CEO exhibited more antioxidant activity compared with the control. This could have been due to the presence of different bioactive compounds in the CEO, primarily cinnamaldehyde, contributing to the overall antioxidant potential of the edible films [41]. Xu et al. [42] found similar results in which the antioxidant activity of the chitosan-gum arabic films increased with the addition of CEO. Furthermore, many studies have reported an increase in the antioxidant activity of edible films when incorporated with essential oils [43–45].

#### **3. Conclusions 3. Conclusions**

The current study revealed that CEO has the potential to be used for the development of sodium alginate and acacia gum-based composite films with improved physicochemical properties at optimal concentrations. The findings of the study are likely to be a valuable resource for the development of future edible packaging formulations, as well as for identifying potential applications for different food products. However, further investigations can reveal the impact of adding the CEO on the antimicrobial properties of sodium alginate-acacia gum-based films. The current study revealed that CEO has the potential to be used for the development of sodium alginate and acacia gum-based composite films with improved physicochemical properties at optimal concentrations. The findings of the study are likely to be a valuable resource for the development of future edible packaging formulations, as well as for identifying potential applications for different food products. However, further investigations can reveal the impact of adding the CEO on the antimicrobial properties of sodium alginate-acacia gum-based films.

#### **4. Materials and Methods 4. Materials and Methods**
